Cracking of hydrocarbon oils with a silica-alumina catalyst containing gallium oxide



United States Patent The present invention relates to the preparation of improved cracking catalysts containing silica and alumina.

This case is filed as a divsion of Gladrow et al. Serial No. 61,340, filed October 10, 1960.

According to the present invention, stable silicaalumina cracking catalysts having high percentages of alumina are prepared which are more selective and active than conventional commercial catalysts and more selective and active than catalysts prepared according to the prior art teachings. These new catalysts have a complete dispersion of the alumina and silica in the catalyst, have highacid strength stability and high surface area retention after steaming compared to conventional commercial silica-alumina cracking catalysts.

In one form of the invention the silica alumina gelled composite containing a high percentage of alumina is aged at room temperature for an extended period of time.

In another form of the invention a superior high alumina content silica-alumina cracking catalyst is made by hydrolyzing a non-aqueous mixed solution of organic silica and aluminum compounds, treating with a gaseous acid such as HCl, preferably CO and then with an aqueous solution of an acid.

In another form of the present invention the silicaalumina catalyst containing a high percentage of alumina was prepared by mixing a silica hydrosol with an organic aluminum salt such as aluminum citrate or tartrate.

In another form of the present invention the silicaalumina catalyst containing a high percentage of alumina contained gallium oxide.

In the course of a study of the fundamental properties of cracking catalysts it has been found that, with silicaalumina catalysts, the performance of the finished catalyst in a cracking operation is dependent upon certain properties (physical and chemical) which the catalyst has and which are built into the catalyst by the particular procedure or process used in the preparation of the catalyst. For instance, it has been found that it is important that a catalyst have high acid strength and titer, high stability of surface area and acidity when the catalyst is subjected to steam, and a complete dispersion of the alumina throughout the amorphous silica network so that no alumina crystallites are observed by X-ray diffraction techniques.

Silica-alumina catalysts containing high percentages of alumina and comprising about 0.8 A1 atoms per Si atom or about 40 wt. percent A1 0 have been made by a variety of techniques and their cracking and physical properties studied. Heretofore these catalysts have shown, in general, a higher activity (conversion at a specified feed rate) and a somewhat higher surface area stability toward steam but they have also been notorious for producing more C gas and coke than standard conventional silica-alumina catalysts containing 13% A1 0 In addition all of the prior commercial silicaalumina catalysts containing high percentages of alumina which have been examined by X-ray diffraction have shown crystalline alumina in the composite. Alumina is a cracking catalyst in its own right, but catalyzes 3,242,069 Patented Mar. 22, 1966 cracking by a different mechanism than mixed oxide acidic catalysts, giving high selectivity towards C gas and carbon or coke in the cracked products.

With cracking catalysts of the mixed. oxide type it is essential to have a high degree of dispersion or complete dispersion of the minor oxide component throughout the framework of the major oxide component and to have a high acid strength and high acid strength retention after heating and/or steaming, and high surface area retention after heating and/or steaming.

It has been known for some time that high alumina silica-alumina type catalysts exhibit high activity relative to conventional commercial 13% A1 O SiO catalysts, particularly after steaming. But. this higher activity is obtained at the expense of poor product distribution, inasmuch as the high alumina catalysts made relatively high coke and C gas. X-ray dilfraction patterns of these catalysts have heretoforejalways shown the presence of crystalline alumina. This suggests that the catalyst is not performing as efliciently as it might,

but instead the crystalline alumina cracks independently as a catalyst in its own right. Since alumina alone cracks hydrocarbons to give very high yields of coke and light gases, it is possible that the observed poor behavior of prior high alumina content silica-alumina catalysts could be due to the crystalline alumina present in the catalyst composite. This suggests that an improved high alumina catalyst would be one having a complete dispersion of the alumina (by exhibiting the lack of any crystalline alumina).

We have found recently also that the acid strength and titer of the active catalytic centers contribute to the quality of the products inasmuch as acidity bears on the relative amounts'of the various reactions occurring in the over-all cracking operation. This has been shown to explain the difference in the octane'numbers of gasolines produced from the same feed stock using catalysts of different acid strength. Conventional SiO Al O catalyst containing 13% A1 0 has its acid strength and titer degraded by heat and steam so that activity is lost rather rapidly in a continuous cracking operation. It is apparent, then, that an improved catalyst over conventional SiO Al O (13% A1 0 catalyst should have a higher acid stability while retaining acid strength when subjected to heat and/or steam.

Surface area of catalysts is an important property, as it represents to some degree the amount of available space to permit reactions to occur. Silica-alumina catalysts in general undergo a continual decrease in surface area when subjected to heat and steam. The rate of surface area decline decreases as the alumina content increases. This suggests, then, that high surface area, and high surface area retention, which can be attained in high alumina sil-icaaalumina catalysts is a very desirable feature.

According to the present invention an improved silicaalumina catalyst is made which contains a high percentage of alumina and which shows no crystalline alumina, has a high acid strength and titer, and a high surface area retention after steaming. With the present invention a silica-alumina catalyst containing a high percentage of alumina is produced which has improved selectivity and activity. One method for making such a catalyst employs an aging step carried out at room temperature for an extended period of time.

The aging or heat soaking step for the silica-alumina high alumina content catalyst is carried out after the silica-alumina composite or gel has its pH adjusted to the range of 6.0 to 8.0, preferably to about 7.0. Within minutes after adjusting the pH the composite undergoes gelation. The aging is carried out at room temperature for about 10 to 30 hours or possibly longer. During aging the alumina undergoes complete dispersion throughout the silica network which result is not obtained under other conditions.

The present invention is an improvement on Kimberlin et al., Patent 2,798,857, granted July 9, 1957. Following the general steps of this Kimberlin et a1. patent and including the aging step of the present invention produces a highly active and selective catalyst.

EXAMPLE 1 A catalyst comprising about 40% A1 and 60% by weight of SiO was prepared by mixing about 4.0 liters of freshly prepared silica hydrosol (3% SiO made by percolating sodium silicate solution over an acid form cation exchange resin, with about one liter of 0.4 N NH OH solution. The silica hydrosol may have a pH between about 8 and 11.

The resulting silica hydrosol had a pH of about 8.5. To this mixture were added 0.92 liter of an anhydrous aluminum amylate solution (87 g. A-l O /l.) using rapid and efficient stirring. The aluminum amylate solution was prepared by dissolving 10 pounds of aluminum metal in 23 gallons of a 5050 mixture of mixed amyl alcohols and petroleum naphtha, the naphtha boiling in the range of 200 F. to 300 F. according to the method described in US. Patent 2,636,865 (taken from column 3 of Patent No. 2,798,857).

Stirring was accomplished by means of a propeller as set forth in Patent No. 2,798,857. By thus mixing the silica hydrosol and the anhydrous aluminum amylate solution with stirring, a hydrous slurry of silica-alumina particles was formed having a pH of about 8.55. After continued stirring for about minutes, 7.2 cc. of glacial acetic acid were added to lower the pH to about 7.0. After further continued stirring for about 4 or 5 minutes, the slurry set to a stiff gel. The alcohol and hydrocarbon selvent were drained ofl? and rejected.

The gelled catalyst composite after standing for about an hour was ovendried at a temperature of about 250 F. for about 16 hours and then calcined for about 16 hours at about 1000 F. This catalyst is designated A and is a catalyst made without the aging step according to the present invention. This example also shows that the composite should not be dried before aging.

EXAMPLE 2 Another catalyst comprising about 40 wt. percent A1 0 and '60 wt. percent SiO was prepared according to the steps set forth in Example 1 up to the preparation of the gel composite having a pH of about 77.0. The gelled silica-alumina catalyst prior to drying was left at room temperature (about 80 F.) for about 24 hours and then oven dried at 250 F. for about 16 hours. The dried gel was then calcined 16 hours at about 1000 F. This cata lyst is designated B and sets forth one catalyst of the present invention. This catalyst also shows the advantage of not drying the catalyst before aging.

EXAMPLE 3 Another 40 wt. percent Al O 60 wt. percent Si0 catalyst was prepared according to Example 2 except that after gelling at a pH of about 7.0, the gel composite was heat soaked for 3 hours at about 190 F., then cooled to room temperature (about 80F.) and left at room temperature for about 24 hours. Then the gel composite was oven dried at about 250 F. for about 16 hours. The dried gel composite was then calcined for about '16 hours at about 1000" F. This catalyst is designated C.

EXAMPLE 4 The catalyst of this example is commercial conventional 13 wt. percent Al O -87 wt. percent SiO catalyst and is believed to be made by making a pumpable slurry of sodium silicate at a pH of about 7.0, impregnating the slurry with acid aluminum sulfate, ammoniating to restore the proper pH to precipitate the alumina and then spray drying. This catalyst was calcined for about 16 hours at atmospheric pressure at about 1000 F. This catalyst is designated D. This catalyst is not a high alumina content silica-alumina catalyst.

EXAMPLE 5 Portions of catalysts A, B, C and D were steamed 24 hours at 1050 F. and atmospheric pressure and were examined by X-ray diffraction to determine if any alumina crystallites were present. The results are given in Table 1.

Table 1 Catalyst A B C A1203 Crystallites present Yes No Yes No The catalyst B of the present invention showed no A1 0 crystallites along with the conventional low alumina silica-alumina catalyst.

EXAMPLE 6 Acid Titer, Milliequivalcnts/g.

4O Acid Strength, Percent H2804 equiv 48 48-71 71-9l 91 Total A, fresh- 0.00 0.06 0.57 0. 63 A, steamed 0. 00 0.33 0.00 0. 33 B, freslL. 0.00 0.00 0.07 0. 48 0.55 B, steamed..- 0.01 0.03 0.29 0.02 0. 35 C, fresh 0.00 0.00 0. 16 0. 42 0.58 C, steamcd 0.00 0. 10 0. 17 0.00 0.27 D, fresh 0.00 0.00 0.00 0.38 0.38 D, steamed 0.00 0.05 0. 08 0.00 0.13

EXAMPLE 7 Portions of the fresh and steamed catalysts A, B, C and D were examined for cracking performance using pure cetane feed at 900 F. The results with the fresh catalysts are summarized below. The w./hr./w. is weight of feed per hour per weight of catalyst.

Catalyst A B O D Conversion, percent 50. O 50.0 50. 0 50. 0| \V./l1I./W 4. 3 7. 1 3. 1 4. 1' (Ii-gas yrcld, wt. percent 12. 4 9. 7 11.0 11.0

Thus it is seen that the catalyst B of the present invention is more active and selective than any of the othercatalysts.

The catalysts A, B, C and D were tested after steaming for about 24 hours at about 1050 F. and

Catalyst B Catalyst B is more active than the other catalysts.

The preferred catalyst .B" was compared with a standard commercial 25% Al O 75% SiO cracking 1 catalyst in a fixed bed test with a gas oil.feed. The

catalysts were shaped into by pellets and steamed at1050 F., 16 hours, 0 p.s.i.g. before testing.

C0nditi0ns.East Texas Light Gas Oil feed, 950..F., 2 v./v./hr., 30 min. cycle (v./v./hr. is volume of liquid :feed per volume of catalyst per hour) 6 *EXAMPLE; 11

The catalystin this example is a commercially available material comprising 13% Al O 87% SiO and similar to catalyst D of Example 4. This catalystwas subjected to an atmosphere of steam. at 1050" F., .0 p.s.i.g., for 24 hours. This catalyst is designated catalyst E.

EXAMPLE: 12

A solution .waspliepared byad m ixing 416 g. ethyl silicate and 1600 m1. Pentasol (mixed amyl alcohols).

To this organic solution were added,. with stirring, 920 ml. of an anhydrous aluminum alcoholate solution (equivalent concentration 87 -gr. A1 0 .per liter) in Pentasol. After stirringwfor an additional 10 minu tes, dry HCl gas was bubbled into the solution or mixture for about 5 minutes atroorn temperature. The mixture or composite organic solution was left standing for 48 hours at room temperature and thenihydrolyzed by slow addition with rapid stirring to a vessel containing 4000 APercent with respect to 25% A1203 standard catalyst AConversion ANaphtha AGas ACarlJon *Research O.N. +3,ml'. T.E.L.

These results show that catalyst B of the present invention gives a much higher conversion than the standard catalyst, along with improved selectivity as is shown by thehigher naphtha yield, lower gas and carbon production, and slightly higher octane number. Once -again it is demonstrated that superior performance is obtained with catalyst ,B of the present invention.

EXAMPLE 8 A catalyst comprising Al O -65% SiO was prepared in the preferred manner as given in Example 2 with the proportions changed to give a 35% Al O Instead of using 4.0 liters of silica hydrosol, about 4.9 liters of silica hydrosol were used. This catalyst is designated B-1. This catalyst was steamed for 16 hours at 1050 F. at atmospheric pressure.

EXAMPLE 9 A standard commercial 25 Al O -75% SiO catalyst was steamed for 16 hours at 1050 F. at atmospheric pressure. This catalyst is designated B-2.

1 EXAMPLE 1O Catalysts A, B-l and Bl-2 were compared in a fixed bed cracking test with-the following results.

C0nditi0ns.-East Texas Light Gas Oil feed, 950 F., 2 v./v./hr., 30 min. cycle ml..H O and 25 ml. concentrated HCl to form. a slurry of gelled silica-alumina particles.

The mixture was then heat soaked .for' 3 hours at 170-190 F., cooled .to room temperature and the pH adjusted to 6.8 by addition of NH OH and then oven dried at 250 F. The catalyst composite was calcined 16 hours at-1000 F. in ambient air. and. then placed in a vessel and subjected to-an atmosphereof steamiat 1050 F., 0 -p.s.i.g., for 16 hours. iThis catalyst comprises 40% Al O 6O% S10 andis designated catalyst F.

The proportions of the chemicals used in Example 12 can be varied to give asilica alumina catalyst containing betweenabout 10 and 50% alumina by weight.

EXAMPLE 13 Catalysts E and F were titrated. bythe method of Benesi (J.A.C.S. 78, 5490 (1956).; also J. Phys. Chem. 61, 970 (1957)) using butyl amine in a non-aqueous system and show the following relations.

Acid Titer, Meq./g.

Acid Strength Region,

Percent H 80 48 48-71 71-91 91 Total Catalyst E 0. 00 1 0.05 0. 08 0.00 0. l3 Catalyst F 0. 00 0.00 0. 13 0. l3 0. 26

APercent with respect to 25% standard catalyst (B-Z) Catalyst AConversion ANaphtha AGas ACarbon i AO .N.*

*Research +3 ml; T.E.L.

These results show that a catalyst prepared according to this form of the invention gives higher activity and conversion, with an improved product distribution compared to the commercial 25 Al O catalyst. The preferred catalyst yields more naphtha, less carbon and gas, and gives a higher octane number than either the standard catalyst 13-2 or catalyst A. This is believed to be due to the improved dispersion of the A1 0 in the catalyst prepared according to the present invention.

Thus it is seen that the catalyst of the present invention, F, shows a much higheracid titer after steaming than commercial catalyst E and in-addition..the remaining acid centersare at a much higher acid strength level.

Catalyst fE and F were also examined by X-ray diffraction methods to see if any crystalline aluminawas present inthe composite. Neither catalyst showed the presence of crystalline A1 0 7 EXAMPLE 14 Catalysts E and F were tested in a cracking operation feeding pure cetane (N-C H at 900 F. The following results were obtained.

At 45% Conversion Percent Percent C Gas Catalyst E 2. 2 8.8 20 Catalyst F 3.0 8.6 20

These data show the catalyst of the present invention is more active than the standard commercial catalyst and shows as good, if not better, selectivity characteristics.

EXAMPLE 15 Percent original surface area retained Catalyst E 45 Catalyst F 93 Thus, the vastly improved stability of the catalyst of the present invention to surface area loss by steam is demonstrated.

EXAMPLE 16 The preferred catalyst F was compared to standard commercial 25% Al O -75% SiO cracking catalyst (B-2) in a fixed bed test with the following results. Each catalyst was steamed at 1050 F., p.s.i.g., 16 hours prior to the test. Conditions: East Texas Light Gas Oil feed, 950 F., 2 v./v./hr., 30 min. cycle The chloride content of the catalyst upon steaming is negligible. This indicates that the high activity of the catalyst of the present invention is not due to aluminum chloride in the catalyst.

In brief compass, this form of the present invention entails a simple and convenient method for preparing high alumina silica-alumina catalysts which are highly active and selective, and have the desirable properties of high acid strength and titer, low attrition rate, and good dispersion of the components throughout the catalyst composite. This method comprises (1) the formation of a homogeneous non-aqueous solution of the silica and alumina precursors, and (2) hydrolysis of the mixture to effect good dispersion of the components amongst each other. Catalysts so prepared have outstanding catalytic, physical and chemical properties.

In another form of the invention using organic silica and aluminum compounds the gaseous acid used is carbon dioxide. The CO gas causes partial gelation of the alumina and silica micelles and subsequent hydrolysis of the gel composite in a dilute aqueous acid solution followed by drying and calcining produces a superior catalyst. All acidic gases are not the equivalents of HCl gas or CO gas as will be shown hereinafter.

Carbon dioxide gas possesses decided advantages over HCl gas that make it a preferred material to use in manufacturing catalysts according to a method of the present invention. For example, no washing of the catalyst is required as there is when using HCl to remove residual chloride. Also the CO gas may be injected under pressure and subsequently recovered and recycled. The possibility of catalyst contamination from equipment corrosion is eliminated. In addition there is an economic and health advantage in using CO Catalyst E from Example 11 will be referred to in the next group of examples for purpose of comparison.

EXAMPLE 18 416 grams ethyl orthosilicate were diluted with 1600 cc. Pentasol. To this were added, with stirring, 920 cc.

A percent with respect to 25% A1203 standard catalyst (B-2) A conversion A naphtha A gas A carbon Catalyst F +13. 9 +3. 5 -3. 0

Research O.N. +3 ml. T.E.L. These results shown that this catalyst F of our invention gives a much higher conversion than the standard catalyst, alongwith higher yield of naphtha, lower gas and carbon, and a slight increase in octane number.

EXAMPLE 17 For regeneration of cracking catalysts, it is preferred that they have a large pore volume. In this catalyst of the present invention the pore volume may be varied by controlling the amount of dry HCl which is added during the preparation of the catalyst. Thus, with the addition of more dry I-ICl, the pore volume increases. The amount of dry HCl referred to in Example 12 and below as limited addition is not sufficient to cause gelation of the catalyst composite and when addition is complete, the solution remains clear. However, if additional dry HCl is added (approx. 15 minutes of addition), the solution becomes cloudy and the material begins to gel. This degree of HCl addition is referred to as complete saturation in the example below.

Chloride content after steaming 16 hours, 1,050" F., O p.s.i.g,

aluminum alcoholate solution (equiv. to 87 gr. Alzog/ liter). The composite solution was then hydrolyzed in 4 liters of water containing 25 cc. concentrated HCl. The aqueous slurry was aged 16 hours at room temperature and then oven dried at 250 F. The oven dried material was steamed 16 hours at 1050 F. and atmospheric pressure. This catalyst comprises 40% Al O 60% SiO and is designated G.

EXAMPLE 19 416 grams ethyl silicate were diluted with 1600 cc. Pentasol. To this are added, with stirring, 920 cc. of

EXAMPLE 20 416 grams ethyl silicate were diluted with 1600 cc. Pentasol, T 0 this solution are added, with stirring, 920

oven dried at 250 F. The material was thensteamed for 16 hours at 1050 Fraud atmospheric pressure. This catalyst comprises 40% Al O 60% SiO and is designated I. It is one of the improved catalysts of the present invention.

EXAMPLE 21 Portions of catalysts E, G, H and? after steaming were titrated by the method of Benesi (J.A.C.S. 78,

5490 (1956)) to determine their acid strength distributions.

Acid Titer, Meq./g. Acid Strength, percent H1304 equiv.

48 48-71 71-91 91 Total Catalyst E 0.00 0.05 0.08 0.00 13 Catalyst G 0. 02 0. 00 0. 00 0. 00 0.02 Catalyst IL. 0.07 0. 00 0. 00 0. 00 0. ()7 Catalyst I 0.04 0.02 0.23 0. 00 0. 29

These data show the superiority in acid strength stability of catalyst I over the other catalysts, including the standard commercial catalyst E. The data also show the ability of CO when added to the mixed organic solution of ethyl silicate and aluminum alcoholate in.the preparation of the catalyst to impart superior acidity compared to S0 or no added gases. This high acidity stability makes itself manifest in the cracking operation.

The proportions of chemicals used .in preparing the catalyst of Example 20 can be varied to give a silicaalumina catalyst containing between about and 50% by weight of alumina.

EXAMPLE 22 In the catalyst of this form of the invention, the use of CO olfers further advantage. A catalyst made employs ing dry HCl such as catalyst F has good attrition properties, better than standard catalyst E. However, the use ofCO in a catalyst such as catalyst .I. greatly increases the catalyst strength, as shown by lower attrition rate as shown in the following tabulation.

Standard roller attrition rate,

Catalyst: percent/hr.

Standard catalyst E" 3.7 Catalyst F employing dry HCl 3.4 Catalyst 1 employing CO 2.4

EXAMPLE 23 Catalyst 1 of our invention, prepared from ethyl silicate and aluminum alcoholate withadded CO was compared in a standard cetane cracking test with standard catalyst E. Both catalysts were steamed at 1050 F., 0 p.s.i.g., .for 16 hours prior to the test. Theresults are summarized below.

W./hr./w. to give Catalyst: 40% conversion Standard catalyst E 2.3 Catalyst 1 6.3

The yields of carbon and naphtha were essentially equivalent to the standard catalyst at these conversions '10 but the yield of C dry gas was lower, 8% vs. 9% for the standard catalyst E at 45% conversion.

Another highly active, selective, attrition resistant catalyst comprising silica-alumina was made by mixing silica hydrosol and an aluminum salt of an organic acid such as citric or tartaric. By means of this procedure any alumina content can be made and the resulting catalyst requires a minimum of washing or none. The catalyst is stable toward heat and steam and is more active than conventional silica-alumina cracking catalyst and just as selective. The catalyst is prepared from an organic acid salt of aluminum and an ammoniacal silica hydrosol.

Catalyst E from Example 11 will be referred to in the following examples for purposes of comparison.

EXAMPLE 24 An improved high A1 0 (40%)Si0 cracking catalyst was prepared as follows. Four liters: of a freshly prepared 3% silica hydrosol were added to one liter of a 0.33 N NH OH solution with stirring. The pH of the solution was 8.5 to this sol solution was added slowly a solution comprising 340 g. aluminum citrate, ml. conC. NH 'OH and 2 liters of water using good stirring. The mixture beganto gel within minutes and CO (as 100 g. Dry Ice) was added to aid gelation. The final pH of the mixture was 6.0. The mixture was allowed to age 48 hours 'at;roorn temperature and then dried at a temperature of 250 F. The catalyst was steamed for 16 hours at 1050 F.,.0 p.s.i.g. before testing. This steam treatment simulates plant catalyst deactivation. This superior catalyst will hereafter be called catalyst J.

EXAMPLE 25 Catalysts E and J were tested for cracking activity by feeding cetane at 900 F. in a 10 minute cycle. Each of these catalysts had been steam deactivated at 1050 F., 0 p.s.i.g. for 16 hours prior to testing. The results are shown below.

W./ Hr./W. to Gas Make Naphtha Catalyst give 43% at 43% Make at Conversion 43% The surface acidity of catalysts E and J was determined by titration in a non-aqueous system with butylamine. The results for the acidity measurements, after steam treatment, for these catalysts are given below.

Catalyst: Acidity, meq./ g. E 0.13 J 0.22

Again the superior high A1 O -SiO catalyst J shows its higher activity as shown in Example 25 in the higher surface acid titer.

EXAMPLE 27 A further example of the higher stability of the high A1 0 catalyst T is shown in the percent retention of surface area after steam-ing as in Example 18. This is indicated below.

Percent original surface area y retained after steaming EXAMPLE 28 A further desirable characteristic of a good cracking catalyst is a low attrition rate. Each of these materials 1 1- was given a standard roller attrition test and the results are shown below.

Catalyst: Percent attrition in 1 hr. E 3.7 J 2.7

Thus it can be seen that a superior high M content sil=ica-alumina cracking catalyst may be prepared from the aluminum salt of an organic acid and a commercial silica hydrosol. This catalyst combines high activity with normal product distribution, stability, and improved catalyst strength.

Another highly active cracking catalyst showing a high selectivity to aromatic hydrocarbons and C plus naphtha contains a minor amount, up to of gallium oxide in a high alumina content silicaaalumina catalyst. Dry gas yields on a weight basis are comparable or less than conventional silicaalumina catalyst containing about 13% alumina. This catalyst has a high acid titer and acid strength, as well as high surface area, low attrition rate, good heat and steam stability.

It is desirable to get complete dispersion of the alumina throughout the silica hydrogel or gel lattice so that there are no residues of crystalline alumina dispersed through the catalyst composite. In addition to these desirable physical and chemical properties it has been 'found that the cracking pattern of the catalyst can be changed or altered to favor the production of a higher proportion of naphtha of higher aromatic content without an increase in the yield of dry gas (wt. basis).

The catalyst may contain up to 10% by weight of gallium oxide, but preferably about l5% gallium oxide is used. The catalyst contains between about 10 and 50% alumina and the rest silica. It is preferred to add the gallium oxide at the time of mixing the solutions to produce the composite catalyst and not by impregnating an already finished silica-alumina gel or catalyst. This catalyst has the unexpected property of producing high aromatic content gasoline in a cracking operation. The catalyst may contain 20-45 parts by weight of alumina, 79-55 parts by weight of silica and l-10 parts by weight of gallium oxide.

EXAMPLE 29 The catalyst of this example is the standard commercial catalyst comprising 13% A|l 0 -87% SiO and similar to catalyst D of Example 4. It is believed to be made by preparing a purnpable slurry of sodium silicate at pH 7, impregnating with alum, ammoniating, and spray drying, and then calcining 16 hours at 1000 F. This catalyst is referred to as catalyst K in the examples below.

EXAMPLE 30 A fresh 3% silica hydrosol, made by the ion exchange method of Example 2, was prepared and 3.4 liters thereof were admixed with 20 ml. concentrated NH OH and gave a resultant sol having a pH of 9.5. To this were added slowly and with stirring 640 ml. of an aluminum lalcoholate solution (equivalent to 87 gr. A1 O /l.) and hydrolysis effected. To this mixed slurry were added 85 ml. of a solution comprising gallium chloride (equivalent to 11.5 gr. Ga O The pH was adjusted to 7.0 with NH OH, the composite heat soaked 3 hours at 170- 190 F. and cooled. The pH was readjusted to 7.0 with NH OH and the mixture oven dried at 250 F. and then calcined 16 hours at 1000 F. This catalyst is referred to in the subsequent example as catalyst L. It comprises EXAMPLE 31 Catalysts K and L were each steamed 16 hours at non-aqueous system using the method of Benesi. The results are tabulated.

Acid Titer, Me /g.

Acid Strength, percent H2SO4 equiv.

48 48-71 71-91 91 Total Catalyst K 0.00 0.05 0.08 0.00 0.13 Catalyst L 0.03 0.00 0.13 0.00 0.25

Thus it can be seen that the improved catalyst L of this invention is much more acidic than conventional catalyst K.

EXAMPLE 32 Catalysts K and L after steaming as in Example 31 were tested in a cracking operation at 900 F., 10 minute cycle, using pure cetane feed. The following results were obtained.

Catalyst K L Conversion, wt. percent 31. 5 81. 5 W./Hr./W 3. 6 5. 2 03- Gas, wt. percent. 5. 7 5. 3 C5 Naphtha, wt. percent. 15.0 15.6

Catalyst L of the present invention is much more active than K while giving some less gas and some more naphtha than catalyst K. It should be stated, however, that the C gas from catalyst L contained considerably more hydrogen than that from catalyst K but this is not reflected on the weight percent data in the table above.

EXAMPLE 33 EXAMPLE 34 Catalysts K and M were tested in a fixed catalyst bed reactor for their cracking properties using an East Texas Light Gas oil feed, 950 F., and 30 minute cycle. The naphtha quality data follow.

Catalyst K M Conversion, wt. percent 50.5 50. 5 Aromat cs in naphtha, wt. percent 25 35 Olefins 1n naphtha, wt. percent 35 29 The gas densities of the C materials from both catalysts were in the range of 1.0l.l based on air density equal to unity. Thus it is seen that with as little as 1% Ga O added a marked increase in aromatics is produced with no change in gas density.

This form of the invention includes a high alumina silica-alumina catalyst, a minor amount of gallia, preferably l5% which results in a catalyst producing naphtha of enhanced aromatic content with very little change, if any, in the weight of C gas and C naphtha yield.

The silica-alumina catalyst of the present invention may be made to contain between about 10% and 50% by weight of alumina.

What is claimed is:

1. A process of cracking hydrocarbons to produce motor fuel which comprises contacting a high boiling hydrocarbon oil under cracking conditions with a catalyst containing 20-45 parts by weight of alumina, 79-55 parts 13 by weight of silica and 1-10 parts by weight of gallium oxide.

2. A process of cracking hydrocarbons to produce motor fuel which comprises contacting a high boiling hydrocarbon oil under cracking conditions with a catalyst containing 33% A1 62% S10 and 5% Ga O 3. A process of cracking hydrocarbons to produce motor fuelwhich comprises contacting a high boiling hydrocarbon oil under cracking conditions with a catalyst containing at least 30% alumina, 1-10% gallium oxide and the rest silica.

4. A process of cracking hydrocarbons to produce motor fuel which comprises contacting a high boiling hydrocarbon oil under cracking conditions with a catalyst consisting of a major proportion of silica, at least 30% of alumina and 110% of gallium oxide.

References Cited by the Examiner UNITED STATES PATENTS 7/ 1957 Kimberlin et a1 252-453 5/ 1959 Winyall 208 DELBERT E. GANTZ, Primary Examiner.

ALPHONSO D. SULLIVAN, PAUL M. COUGHLAN,

Examiners. 

1. A PROCESS OF CRACKING HYDROCARBONS TO PRODUCE MOTOR FUEL WHICH COMPRISES CONTACTING A HIGH BOILING HYDROCARBON OIL UNDER CRACKING CONDITIONS WITH A CATALYST CONTAINING 20-45 PARTS BY WEIGHT OF ALUMINA, 79-55 PARTS BY WEIGHT OF SILICA AND 1-10 PARTS BY WEIGHT OF GALLIUM OXIDE. 